1. Technical Field
The invention relates to an electrically conductive composition.
2. Background Art
Electrically conductive compositions, such as gels, creams or jellies, have found utility in providing electrical connection between various locals. For example, it is customary for persons involved in the manufacture of integrated circuits and other sensitive electronic components to wear wrist straps that are electrically connected to ground to guard against the accumulation of electrostatic charges. U.S. Pat. No. 4,398,277 discloses one such wrist strap which comprises a fabric wrist band which holds an electrically conductive stainless steel plate against the wearer's wrist. A wire conductor provides an electrical path from the metal wrist plate to ground. Additionally, the fabric wrist band is electrically conductive due to the presence of silver-plated filaments in the fabric. These filaments provide a continuous electrical path from the wearer's wrist to ground even if the stainless steel plate accidentally moves out of contact with the wearer's wrist.
The use of a moisturizer, such as a skin lotion, is recommended to ensure good electrical contact between the wearer's body and the wrist strap, particularly in dry (e.g., low humidity) conditions. The use of moisturizers has, however, proven to be unreliable for this purpose as they tend to lose their skin-moistening effect upon evaporation of the water present in them. Additionally, both perspiration and moisturizers contain materials such as salts that can be corrosive to metals and which may, over a long period of time, gradually attack both the face of a stainless steel wrist plate and the silver plating of the filaments thereby reducing the electrical conductivity of the strap. Even a small reduction in electrical conductivity of the wrist strap is a major concern since the loss of conductivity could allow a sudden electrostatic discharge from the wearer to an electronic component being handled. Such a discharge could damage the component thereby either rendering it inoperative immediately or causing it to fail prematurely.
Electrically conductive compositions, such as gels, are in widespread medical use for ensuring good electrical contact between the skin and electrodes such as are used in EKG tests. These compositions generally comprise humectants, bactericides, thickeners, water and electrolytic salts which enhance electrical conductivity. The use of such salts is detrimental to the long term efficacy of the wrist strap due to the corrosive effect they would have on the metals in the strap. Moreover, the water present in such compositions tends to evaporate within a small fraction of a typical wearing time encountered in the manufacture of integrated circuits. This would require frequent reapplication of such compositions thereby magnifying the problems caused by the presence of the salts, and adding to the inconvenience in using the strap.